Photocatalytic generation of hydrogen under extreme conditions

Advanced spectrometry in satellite orbiters have revealed the presence of water on the Lunar surface. Lunar water can be utilized in water splitting to produce oxygen and hydrogen. Photocatalysis, a light assisted catalysis that absorbs energy from light and drives chemical reactions can be used for splitting lunar water, to produce oxygen that can be used by astronauts and hydrogen can be used as a fuel for deep space exploration. Without an atmosphere to absorb light, the cumulative photon flux reaching the lunar surface is 1.4 times greater in comparison to earth. It is calculated that 0.33 kg of H2 and 2.68 kg of O2 could be produced per m2 per lunar synodic month (29.35 earth days) using TiOx coated Al:SrTiO3, in comparison to 0.03 kg of H2 and 0.21 kg of O2 at earth equator, which is 8 times greater than over the same time-period . In the current project, we aimed to replicate extracted water from lunar regolith(soil) and environmental conditions of the Lunar south pole and demonstrated photocatalysis using Al doped strontium titanate (Al:SrTiO3) or TiO2 derived from lunar regolith simulant. We successfully demonstrated. Low temperature photocatalysis at 3 °C. Water splitting occurred at water vapour pressure of 23 mbar. Photocatalysis was demonstrated using desorbing water from frozen hydrated lunar regolith. Production rate increased with decrease in temperature and was higher when photocatalysis was performed at the vapour pressure of water. The lunar regolith is a source of many minerals such as iron, titanium, calcium and magnesium. Extraction of titanates is of special interest, as they are active photocatalysts. Lunar regolith simulant depicts minerology around the lunar south pole, with 4.5% of ilmenite, a mineral of iron and titanium. To demonstrate in-situ resource utilization, we explored the acid leaching of ilmenite to obtain photoactive nanoparticles. We then extended this process with necessary adjustments to convert lunar mare regolith simulant (LMS) into a photoactive product. The resulting material was characterised by scanning electron microscopy, powder x-ray diffraction and ultraviolet-visible diffuse reflectance spectroscopy, to establish morphology, crystal structure and band gap. The photocatalytic activity of the materials was studied by liquid phase water splitting experiments under sacrificial conditions using 1:1 methanol: water solution under 365 nm illumination could produce hydrogen at the rate 4.23x10-2 μmol /h and oxygen at the rate of 2.53x10-1 μmol /h. We have demonstrated low temperature, low pressure photocatalysis using water from hydrated regolith, and photo active material derived from regolith simulant. Hence, photocatalysis is a promising technology to produce oxygen and hydrogen on the moon for human habitation.